Sameer Puri Many studies have shown that when you have anterior teeth in occlusion, there is a certain amount of flex to the teeth. Dentin by nature is flexible. The enamel gives the tooth its stiffness. By having the two components of the teeth work in harmony, you get the natural flexion in a tooth which has the proper amount of flexibility and stiffness that allows teeth to function appropriately.
Many studies have also shown that on posterior teeth, one should do full cuspal coverage after endodontic therapy. There have been too many cases where a simple inlay or onlay was completed after endodontics and the tooth ended up with a catastrophic failure. Posterior teeth need full cuspal coverage after endodontic therapy.
So if we take these two concepts and apply them to anterior teeth, what then should be the conclusion? Should an anterior tooth that has had endodontic therapy be restored with a full coverage crown? If you look at the case pictured, the patient suffered a traumatic injury of the anterior teeth requiring root canal therapy of the left central incisor #9 (tooth 2-1 in the international numbering system).
Should the tooth pictured below receive a full coverage crown? The answer is no. Concerning the studies regarding full cuspal coverage, the conclusion of covering all the cusps only applies to posterior teeth. With anterior teeth, we want to avoid full cuspal coverage if at all possible. The reason is that if we go back to the concept of flexibility of the tooth, what keeps the tooth from “over flexing” and over stressing is the cingulum. The cingulum provides support and resistance for the tooth. A clinician then should do all they can do to not prep away the cingulum.
Look at the preparation design for both teeth. Both teeth have been prepared to receive porcelain veneers. Both teeth have been prepared in a manner that tries to avoid cutting away the cingulum. If the cingulum was removed, the tooth would be significantly weaker and perhaps suffer additional trauma or damage in the future. The conclusion is quite simple- if you can avoid it, try not to cut away the cingulum. If you can avoid it, avoid full coverage preparations on anterior teeth if at all possible.
By no means does this mean that we never do full coverage. Of course there are times that we have no choice. Replacing existing crowns, restoring extensively broken down teeth, changing the vertical dimension or occlusion all require that we do a full coverage of the anterior teeth. I would argue however, there are plenty of other times that clinicians from force of habit just prepare without considering the long term health of the teeth. Bottom line, if at all possible, avoid cutting down the cingulum. You will find that the tooth is infinitely better off in the long run.
